Highly siliceous porous crystalline materials (zeolite), often loosely termed molecular sieves, are well known in the art. They are characterized by their highly ordered crystalline structures and have pores of nearly uniform dimensions. The highly ordered dispersion of alumina (if present) and silica tetrahedra present in the crystals make for a large number of active sites and the uniform pore openings of the zeolites allow for easy ingress of certain molecular structures. Processes for producing zeolites synthetically are now well known in the art. For example, U.S. Pat. Nos. 3,702,886 and 3,941,871 (Re. 29,948) disclose a process for synthesizing ZSM-5 zeolite in which the zeolite material is crystalized from a reaction mixture of selected reactants. U.S. Pat. No. 3,709,979 discloses a related process for preparing ZSM-11 zeolite by crystallization from a reaction mixture. The preparation of ZSM-12 zeolite by crystallization from a reaction mixture is disclosed in U.S. Pat. No. 3,832,449. The preparation of ZSM-23 is disclosed in U.S. Pat. No. 4,076,842. U.S. Pat. No. 4,016,245 discloses the preparation of ZSM-35 zeolite and U.S. Pat. No. 4,046,859 the preparation of ZSM-38. The preparation of ZSM-48 zeolite is disclosed in U.S. Pat. Nos. 4,397,827 and 4,375,573.
The entire contents of U.S. Pat. Nos. 3,702,886; 3,941,871 (Re. 29,948); 3,709,979; 3,832,449; 4,076,842; 4,016,245; 4,046,859; 4,397,827 and 4,375,573 are incorporated herein by reference.
These disclosures in common describe the preparation of zeolites by crystallizing them from a reaction mixture containing sources of an alkali metal oxide, an organic compound, an oxide of aluminum (if added aluminum is desired), an oxide of silicon, and water.
Often in preparing zeolites for use in commercial operations, such as fixed or fluid bed reactors or adsorption systems, the finely divided zeolites can be mixed with a binder material such as clay, alumina, silica-alumina, etc. and formed into porous pellets or fluid particles. In order to achieve maximum dispersion and effectiveness of the zeolite, it is desirable that the zeolite crystallites be as fine as possible and more importantly that they not be agglomerated into relatively larger size particles. Nonagglomerated or deagglomerated crystals are more easily dispersed in the compositing medium and a greater amount of crystallite surface is exposed for catalytic activity if deagglomerated crystals are used.
A primary object of this invention therefore is to prepare porous siliceous crystalline zeolite materials characterized by a minimum amount of agglomeration of the individual crystallites.